A theme for Tree Style Tab that tries to replicate the vertical tab feature of Microsoft Edge Browser
A theme created for Tree Style Tab extension on Mozilla Firefox, that tries to replicate the vertical tab user interface of Microsoft Edge Browser
If you want to also copy the hover feature of sidebar found on Microsoft Edge, then you can use the userChrome.css and other files included on the "edge-mimicry" folder. However, this sidebar mod will remove the resizeable feature since it uses a fixed width configuration.